1. Field of the Invention
The invention relates to a method for controlling a welder with a consumable electrode, wherein the values of the welding parameters required for a welding process are stored in a memory device and saved in the form of so-called characteristic curves by at least one support point per characteristic curve.
2. The Prior Art
In general, it is known from the prior art that, for a welding application, a plurality of welding parameters from which the optimum working point can be composed are adjustable at a welder. In order to make it easier for the user of the welder, several working points are stored as so-called support points in the form of individual points of a characteristic curve. This will enable the user to shift the working point on the characteristic curve substantially by changing the welding parameters such as the welding current, welding voltage and wire feed speed.
Since a plurality of welding applications can be performed by a welder, an accordingly large number of characteristic curves is each stored by several support points in a memory device of the welder for the same base material of the work-piece, diameter of the filler metal, protective gas etc.—at the same material. The user may thus select the appropriate characteristic curve as a function of the welding application. A welding application in this respect is not to be equated with a welding process, but, in particular, will rather depend on the material of the workpiece as well as the filler metal and the type of welding (fillet weld, single V groove weld, butt weld, etc.). Consequently, a plurality of welding applications must be covered by a welding process (pulse, standard short arc, CMT—cold metal transfer welding etc.).
From EP 1 098 729 B1, it is further known that, upon retrieving or adjusting a welding parameter between a minimum and a maximum curve, the control device will determine the set-points of the other welding parameters of this welding process by a computational method and, in particular, an interpolation method. By the interpolation method, the other curves located between the minimum and maximum curves will be determined, with which the welding process will subsequently be performed. Thus, only two characteristic curves, i.e. the minimum and maximum curves, are stored for a welding process and the intermediately located characteristic curves are interpolated. In the end, one characteristic curve will each be used to enable the user to shift the working point, as is known from the general prior art.
In doing so, it is, however, disadvantageous that basically one characteristic curve is required for each welding application. It is true that such characteristic curves in most cases are not created by the user, but supplied by the manufacturer of the welder, or individually tailored for the respective welding application on the user's request. A reason for this is also that, in most cases, not all the welding parameters required for the creation of a characteristic curve or its support points will be available to the user. Consequently, each characteristic curve involves costs and time. If a welding application changes slightly, no optimal welding result will, in most cases, be achieved using the characteristic curve created for this welding application, primarily in respect to the heat input into the workpiece and what is called the filling ratio (i.e., the appearance of the welding bead). This is due to the fact that, when adapting the working point, the latter will always extend on the characteristic curve and the welding parameters like the wire feed speed, the welding current and the welding voltage will change in mutual dependence. The heat input into the workpiece will, in particular, change as soon as the working point is being shifted on the characteristic curve. Consequently, the demands on the weld and, in particular, on the filling ratio and the fusion penetration (which corresponds to the heat input) will not be met. A separate characteristic curve would thus be required for the slightly changed welding application.